﻿/****************************************************************************************
*	Mouzetrap - client/server framework	
*
*	$HeadURL: http://mouzetrap.googlecode.com/svn/trunk/Mouzetrap/Threading/SyncUtilities.cs $
*	$Id: SyncUtilities.cs 11 2009-06-11 09:10:25Z tobz@fallenrealms.net $
*
*	Original copyright Julian M Bucknall (www.boyet.com) 
* 
*	Copyright (c) 2008 Toby Lawrence
* 
*	Permission is hereby granted, free of charge, to any person obtaining a copy
*	of this software and associated documentation files (the "Software"), to deal
*	in the Software without restriction, including without limitation the rights
*	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
*	copies of the Software, and to permit persons to whom the Software is
*	furnished to do so, subject to the following conditions:
* 
*	The above copyright notice and this permission notice shall be included in
*	all copies or substantial portions of the Software.
* 
*	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
*	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
*	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
*	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
*	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
*	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
*	THE SOFTWARE.
* 
****************************************************************************************/

using System.Threading;

namespace Mouzetrap.DataStructures
{
	/// <summary>
	/// Provides common methods used in lock-free structures.
	/// </summary>
	public static class SyncUtilities
	{
		/// <summary>
		/// Compares a value in a location, and swaps it with a new value if the comparand is equal to 
		/// original value.
		/// </summary>
		/// <typeparam name="T">the type of the values</typeparam>
		/// <param name="location">the location of the value to check</param>
		/// <param name="comparand">the value to compare against the original location</param>
		/// <param name="newValue">the value to replace the original value with</param>
		/// <returns>true if the swap succeeded, false if another thread pre-empted the operation</returns>
		public static bool CompareAndSwap<T>(ref T location, T comparand, T newValue) where T : class
		{
			return ReferenceEquals(comparand, Interlocked.CompareExchange(ref location, newValue, comparand));
		}
	}
}